{Blue crab} (Zo["o]l.), the common edible crab of the
Atlantic coast of the United States ({Callinectes
hastatus}).

{Blue curls} (Bot.), a common plant ({Trichostema
dichotomum}), resembling pennyroyal, and hence called also
{bastard pennyroyal}.

{Blue devils}, apparitions supposed to be seen by persons
suffering with {delirium tremens}; hence, very low
spirits. ``Can Gumbo shut the hall door upon blue devils,
or lay them all in a red sea of claret?'' --Thackeray.